The subject invention relates to a method and apparatus for use in dilating occluded blood vessels. More particularly, the subject invention relates to such a method and apparatus in which dilatation is achievable through selective use of first and second balloon means. The invention is intended for use in treating either arterial or venous occlusions.
Prior art efforts for the treatment of occluded blood vessels have relied mainly upon the employment of bypass vessels or some surgical technique whereby the occlusion is physically removed from the vessel being treated. A recent technique for treating occluded blood vessels relies upon the insertion of some type of an instrument into the vessel to dilate the occlusion through a stretching or compressing process. The subject invention is concerned with a technique of the latter type.
There are balloon type dilatation catheters employing invertable-evertable balloon elements at their distal ends. Eversion of the balloon element is accompanied by its linear extrusion through the occlusion zone. Subsequent radial expansion of the balloon element serves to compress or compact the occlusion in place. Balloon elements of this type have generally a low dilating capacity and a low shape retention capacity, tending to elongate and bulge out at the sides of the occluded area when severe radial restriction is offered by hard, fibrous plaque.
Another type of balloon element in such dilatation catheters has been one of the sleeve type in which both ends of the element are anchored. Such a balloon is generally capable of applying a higher pressure to an occlusion and is better able to hold its shape than the invertable-evertable type of balloon element.